Safe and effective drug therapy by injection depends not only upon accurate diagnosis, but also on efficient and reliable introduction of the medical substance into the subcutaneous cellular tissue without introducing contaminants or ambient air. The applicable drug or pharmaceutical must first be drawn from the resident container or vial into a syringe before injection The integrity and features of the vial, therefore, are influential over the overall safety of the injection.
Typically, great care must be taken when a needle cannula of a syringe is used in conjunction with a vial containing a pharmaceutical to be administered to the patient. As the pharmaceutical is drawn out of the container via the needle cannula, precautions must be taken to avoid air being drawn into the syringe. In rigid vials, air must be introduced into the container to fill the void created as the liquid pharmaceutical is withdrawn. This volume of air then becomes susceptible to being mixed with the pharmaceutical or being drawn in through the needle cannula and creating air pockets in the syringe barrel. Catastrophic consequences could result if these air pockets are subsequently injected into the patient along with the liquid pharmaceutical. Also, drawing ambient air into the vial can introduce airborne contaminants to the pharmaceutical.
Problems associated with injections are further complicated when the medication to be administered must be stored as two separate component parts, then mixed, prior to injection. Dual chamber vials have been developed to facilitate storage and mixing of these two-component medications. Common examples of multipart medications include medications which must be mixed from a component A, usually a preservative or catalyst, and a component B, which is usually a pharmaceutical. Component A or component B may be in powder or crystalline form instead of liquid form.
Recently, dual chamber vials have been developed which allow an A component and a B component to remain separated in independent chambers within a single package until mixing is desired. The vial allows mixing of the component parts in that same unitary package. In an example of such a device is the MIX-0-VIAL two compartment vial manufactured by the Upjohn Company of Kalamazoo, Michigan. This device is a single vial container having two chambers separated by a small stopper. The septum is formed by a plunger-stopper at one end which is used to pressurize the contents of one chamber so to displace a plug lodged in a small orifice separating the two chambers. As the plunger stopper is displaced (by giving it an axial push), the plug floats freely into one of the chambers and is used as an agitator to mix the two component parts together. The two components are free to flow between chambers through the connecting orifice and thereby mix together. Although this device is a significant advance in dual chamber vials, the device has a significant disadvantage. Even when the two components are properly mixed, when a needle cannula penetrates the septum and draws out the mixed medication, air becomes entrapped in the vial as air enters to replace the removed liquid as the medication is withdrawn. Time consuming precautions must be taken to carefully avoid entrapping air in the syringe and injecting the same into the patient.
Pharmaceutical components are sometimes sensitive to how violently they are mixed. For example, certain lyophilized crystals of human growth hormone, when mixed with a liquid carrier, must be mixed slowly. Mixing too quickly can cause damage to the pharmaceutical. The mechanical crushing, shearing and tearing, which can accompany rapid mixing, break up the molecules into subcomponents which do not retain the same medical qualities.